As I said earlier, you WILL want good insurance coverage.
Bare logs are harder to ignite than OSB. I don't know how varnish/stain on the logs or paint on the OSB might change that.
When I arc-weld, the welder throws sparks. When I use a grinder, the grinder throws sparks. Same with high-speed sanders. I have an Oxy-acetylene and a propane torch that I heat, braze, weld, and solder with. I have been known to use the propane torch to melt-out rubber control arm bushings, which throws sparks and ignited rubber vapor.
The only part of that that I do in the house is soldering of copper pipes, and I haven't done that for nearly twenty years. When I did, I had metal heat shields protecting the wood.
It is not impossible for electric motors to overheat and catch fire; I've had it happen twice on "loaner" blow-in-insulation machines, although admittedly they weren't in the garage at the time. Point being, a large electric motor on an air compressor or other device could fail and flame.
Just doesn't make sense to use OSB when "sheetrock" gypsum board is known to be fire-resistant and essentially required as part of fire code.
'Course, if you want to substitute "Durock"-style cement board, I won't object.